Passivation of black phosphorus nanoflakes embedded in a silica glass matrix affords ambient saturable absorption stability enhancement.

Black phosphorus (BP) is a graphene analogue with ultrafast broadband nonlinear optical properties that make it a promising nanomaterial for saturable absorption. However, BP nanoflakes chemically degrade in ambient conditions. We developed air- and photo-stable BP nanoflakes via incorporation in inorganic-organic hybrid matrices. This realized passivation and materialization through a sol-gel method that produced high-quality, transparent bulk materials. Saturable absorption parameters of the passivated BP were maintained after five months in ambient storage and after 8000 300 µJ nanosecond laser shots. The nonlinear absorption coefficient was still 62% after 12 months in open air, which was higher than that for non-passivated BP after three days. The stability was attributed to dense silica-gel glasses that enveloped the BP, essentially eliminating oxygen and water penetration. The simplicity of this approach may stimulate potential applications for environmentally sensitive high-performance solid-state devices.